1. Field of the Invention
The present invention relates to an axial flow fan for an air conditioner, and in particular to an axial flow fan for an air conditioner which is capable of changing the shape of blades by varying a design factor such as a chord length, a sweep angle, etc., generating an enough flowing amount of a fan for implementing an efficient heat radiation of a heat exchanger, and decreasing a noise which occurs during an air flowing operation of the fan, so that it is possible to implement a high efficiency and low noise fan system.
2. Description of the Background Art
An air conditioner is an apparatus capable of processing air and supplying the processed air into a certain interior for thereby maintaining air in a room or a building in a clean state and is classified into an integration type and a separation type.
The above-described integration type and separation type air conditioners have the same functions. However, the integration type air conditioner having an integrated cooling and heating function is installed using a fixing apparatus by forming a hole at a window or a wall. In addition, in the separation type, a cooling apparatus is installed inside a room as an indoor unit, and a heat radiating and compression apparatus is installed outside the room as an outdoor unit. The cooling apparatus and the heat radiating and compression apparatus are connected by a refrigerant pipe.
The separation type air conditioner will be explained.
The separation type air conditioner includes an indoor unit for performing a cooling function, an outdoor unit for performing a heat radiating and compression function, and a refrigerant pipe for connecting the indoor and outdoor units.
The indoor unit absorbs heat in a certain interior, and the outdoor unit radiates heat, which corresponds to a sum of heat absorbed in the interior and heat that a compressor radiates to refrigerant, to the outside.
As shown in FIG. 1, the outdoor unit of the conventional separation type air conditioner includes an axial flow fan 1 for sucking an indoor air, generating a certain flow of air used for a heat exchange by the outdoor unit and discharging air, a motor 3 for providing a driving force to the axial flow fan 1, a compressor 5 for compressing a low temperature and pressure vapor state refrigerant flown from the indoor unit and changing the same into a high temperature and pressure vapor state refrigerant, an outdoor heat exchanger 7 for exchanging heat between the high temperature and pressure vapor state refrigerant and the air sucked by the axial flow fan 1 for thereby condensing the same into an ambient temperature and high pressure liquid state refrigerant, an accumulator 8 installed at a suction portion of the compressor 5 for removing an impurity of the refrigerant and preventing the liquid state refrigerant from being flown into the compressor 5, and a casing 10 for receiving the above-described elements therein.
The casing 10 includes a front panel 11 for forming a front surface of the outdoor unit, and a rear panel 13 for forming both side surface and a rear surface. The rear panel 13 includes a suction port 13a for sucking an external air into the interior of the casing 10, and the front panel 11 includes a discharge port 11a for discharging the inner air of the casing 10 to the outside.
In addition, a protection grille 12 is installed at a portion of the discharge port 11a for preventing an access of the axial flow fan 1 which is rotated at a high speed.
In the drawings, reference numeral 4 presents a shroud 4 which guides the flow of air discharged from the discharge port 11a of the front panel 11 by the axial flow fan 1, and reference numeral 6 represents a noise absorbing material which surrounds the compressor 5 for decreasing noises of the compressor 5.
The operation of the above-described outdoor unit will be explained.
When the refrigerant gas compressed by the compressor 5 is supplied to the outdoor heat exchanger 7, a heat exchange is performed between the supplied refrigerant and the air sucked into the interior of the casing 10 by the rotation of the axial flow fan 1 for thereby condensing the refrigerant into an ambient temperature and high pressure state refrigerant, and the temperature of the thusly sucked air is increased.
The air having the thusly increased temperature is discharged to the outside by the axial flow fan 1.
Namely, the air sucked into the interior of the casing 10 through the suction port 13a of the rear panel 13 of the outdoor heat exchanger 7 is discharged to the outside through the axial flow fan 1 and the discharge port 11a of the front panel 11.
When the compressor 5 compresses the refrigerant, the refrigerant circulates through the indoor/outdoor space connection refrigerant pipe which connects the indoor unit and the outdoor unit, so that the refrigerant is flown into the heat exchanger 7. At this time, as the axial flow fan 1 is rotated by the driving operation of the motor 3, the air is sucked through the suction port 13a, and a certain air flux is formed in the air discharged through the discharge port 11a. The thusly formed flux air contacts with the outdoor heat exchanger 7, so that the refrigerant is condensed.
The refrigerant condensed by the outdoor heat exchanger 7 is adiabatically expanded by an expander(not shown) and is supplied to the indoor unit(not shown) through the indoor/outdoor space connection refrigerant pipe(not shown).
The refrigerant supplied to the indoor unit is heat-exchanged with the air sucked by an indoor fan(not shown) in an indoor heat exchanger(not shown) and is changed into a low temperature and pressure vapor state refrigerant. At this time, the air passed through the indoor heat exchanger has a temperature dropped by a heat exchanger with the refrigerant and is flown into the indoor space for thereby implementing a cooling operation.
Continuously, the refrigerant which is changed to a low temperature and pressure vapor state by the indoor heat exchanger of the indoor unit is moved to the compressor 5 through the indoor/outdoor space connection refrigerant pipe. The above-described operation is repeatedly performed.
In detail, the refrigerant which is heat-exchanged in the indoor unit flows through the indoor/outdoor space connection refrigerant pipe and a service valve mount 14 installed at a portion of the outdoor unit and is introduced into the compressor 5 through the accumulator 8 installed for removing a certain impurity and preventing an introduction of the liquid state refrigerant.
As described above, in the operation of the outdoor unit of the air conditioner, the axial flow fan 1 which generates a certain flux in air is important.
Namely, the axial flow fan 1 is designed so that a certain air flowing amount which is required for enhancing a heat exchanging efficiency between the refrigerant and air is obtained.
In addition, in order to satisfy the need of a customer, the axial flow fan 1 must consume a small amount of electric power. The air flowing noises must be decreased.
In order to manufacture a fan which satisfies the above-described conditions, an intensive study has been conducted for changing the shape of the fan by changing various fan design factors.
There are various fan design factors which determine the shape of the fan. In addition, the effects that the above-described design factors affect the performance of the fan are complicated and various.
As shown in FIGS. 2, 4 and 5, as the fan design factors which may affect the shape of the axial flow fan 1, there are a diameter (2.times.Rt) of an axial flow fan, a diameter (2.times.Rh) of a blade hub, the number and an external dimension of blades 2, a pitch angle .phi. with respect to each blade 2, a maximum chamber (Cmax), a sweep angle .theta., a chord length (1), a rake, etc. In addition, there are a leading edge LE of a blade, a trailing edge TE, and a curvature shape of a blade tip BT.
As shown in FIG. 2, the rake among the above-described dimensions represents a degree that the position of the cross section is deviated in a .+-.Z direction in accordance with the radial position of the blade when viewing the cross sectional from a Z-X plane. The descriptions of the remaining dimensions will be provided as follows.
In the axial flow fan 1 in which the shape of a three-dimensional blade is determined based on the above-described fan design factors, the end portion having a radius relatively larger compared to a plurality of portions of the blade 2 is important for the reason that most flowing amount occurs at a blade tip BT of the blade.
As shown in FIG. 3, as a result of a measurement of a sound intensity at the portion behind the blade 2 of the axial flow fan 1, noises constantly occur irrespective of the radial direction of the blade 2, in particular, irrespective of the portions of the hub or the portions of the blade tip.
Therefore, a portion(hub portion) having a radius relatively smaller compared to a plurality of the portions of the blade 2 of the axial flow fan 1 does not affect an increase of the flowing amount of air. In this case, the power consumption of the motor 3 is increased, and the noises are increased. Therefore, the above-described portion(hub portion) does not affect an air flowing efficiency at a plurality of portions of the blade 2 of the axial flow fan 1 but increases a power consumption and noise occurrence. Therefore, a part of the portion having a smaller radius may be removed for thereby implementing a low noise and high efficiency of the axial flow fan 1.
Namely, the axial flow fan is installed at the outdoor unit for generating a certain air flow flux which is required for the heat exchanger. An intensive study has been performed for optimizing the shape of the axial flow fan in order to decrease the power consumption of the motor used for rotating the axial flow fan and the air flowing noises for thereby enhancing an efficiency of the axial flow fan even when the same amount of air occurs.